Acoustic phased array antenna with isotropic and non-isotropic radiating elements

ABSTRACT

An acoustic phased array antenna system comprising a plurality of omnidirectional receiving elements for addressing close-in fields and a plurality of non-omnidirectional receiving elements for addressing remote fields with the combined elements used to extend the maximum range of the antenna system. The non-omnidirectional receiving elements can be formed by adding focusing structures such as cylindrical or oval lenses in the receiving path of omnidirectional receiving elements. Antennas with a plurality of isotropic radiating and a plurality of non-isotropic radiating elements can be utilized for sonar and ultrasound systems. An acoustic phased array antenna system comprising a first plurality of receiving elements with a first field of view and a second plurality of receiving elements with a second field of view that is at least 50% narrower. An acoustic phased array with a plurality of isotropic radiators and a plurality of non-isotropic radiators to extend the range of the system.

BACKGROUND OF THE INVENTION

Phased Array antennas for electromagnetic (radar and communication) andacoustic (sonar and ultrasound) systems use multiple radiating elements,each radiating electromagnetic waves or acoustic waves respectively. Thewaves radiating from each element of the array on the face of an antennahave their phase and the amplitude separately controlled so that one ormore beams of in-phase radiated waves is projected in a narrow patternin a specific direction. In the case of a linear array antenna such asin a sonar towed array, the beam forming is only in the horizontalplane. In area array antenna with elements distributed in an X-Y grid,such as ship board phased array radar, the beam is formed in both thevertical plane and the horizontal plane. Without phase delays betweenadjacent radiating elements, radiated beam would be broadside orperpendicular to the face of the antenna. By changing the phasedifference between vertical and/or horizontal adjacent elements, thedirection of the beam of in-phase waves is changed in the vertical(elevation) and/or horizontal (azimuth) planes.

In prior art phased array radar systems, the antenna has an array of100's or 1000's of radiating elements, each radiating an electromagneticwave at a specific frequency and wavelength, such as microwave ormillimeter wave or from less than 1 GHz to more than 40 GHz. The radarantenna has radiating elements that have a radiating pattern that isgenerally isotropic covering a field of view of at least +60° to −60° inazimuth and at least +60° to −60° in elevation although in the case ofsurface radar systems the useful field of view in elevation is generally0° to 90°. In most radar systems, the same antenna and the same array ofelements used to radiate the transmitted electromagnetic waves are usedfor receiving the return electromagnetic waves. On the receive mode,these elements are generally omnidirectional, able to receive signalsfrom at least +/−60° in azimuth and at least +/−60° in elevation.

Parabolic Radar Antenna Systems

To fully understand the function of various prior art phased array radarantenna and their resulting radar wave patterns, it helps to understandmonolithic, non-phased array antenna. The basic radar antenna has asingle feed or radiating element, a parabolic reflector and a singlereceiver element. The radiating element typically has a spherical ornear spherical wavefront. Each portion of the of the wavefront reachesthe parabolic reflecting surface and is phase shifted 180°, reflectedoff of the surface at an angle that has each portion of the reflectedwave traveling in parallel paths forming a narrow beam. The parabolicshape of the reflector combined with the radiating element being locatedat focal point F, causes all portions of the radiating wave have thesame path length from the radiating element to the reflector and fromthe reflector to a plane perpendicular to the direction of radiation.All portions of the reflected wave are now in phase and radiating innear parallel paths and forms a narrow radiating beam.

The gain of a parabolic antenna is the ratio of the radiation intensityin a particular direction to the radiation intensity averaged over alldirections. Assuming a uniform antenna pattern, the gain of a parabolicantenna is equal to the area of the isotropic sphere (4πr²) divided bythe area of the beam as measured by the 3 dB point. Different bandwidths can be formed by moving the radiating element away from theantenna focal point. If one assumes a rectangular beam of “a” degreesvertically and by “b” degrees horizontally, the antenna gain isapproximately:

$G = \frac{41250}{ab}( {{where}\mspace{14mu} a\mspace{14mu}{and}\mspace{14mu} b\mspace{14mu}{are}\mspace{14mu}{in}\mspace{14mu}{degrees}} )$

Looking at a number of beam widths, the approximate gain is as follows:

Beam Width (a, b) 1° 2° 4° 8° 16° Gain (Numeric) 41250 10312 2578 644161 Gain dB 46 dB 40 dB 34 dB 28 dB 22 dB

Looking at this one can see that having a smaller beam width can greatlyincrease the power density of the radar signal within radar beam width.The beam is moved by moving the antenna up or down or left or right, orby rotating it to target any location. The draw back of a smaller beamwidth it is that it would take more steps of moving the antenna to covera specific area such as a 360° horizontal sweep and a 90° verticalsweep. This takes more time as the beam gets smaller and limits theagility of the radar system. It should be noted that if as is typical,the receive signals are received by the same parabolic antenna, thereceive gain would nearly equal the transmitting gain.

Phased Array Radar Systems

Prior art phased array radar antennas are composed of an array ofradiating elements, generally uniformly spaced in the horizontal andvertical directions. The exception is linear phased array antenna whichhas elements uniformly spaced horizontally or vertically line forming aline array. Each element of the array is fed an electromagnetic signalthat has its phase (and potentially, its amplitude) electronicallycontrolled relative to its neighbors to form and to steer one or morebeams of in phase electromagnetic wave fronts. The beam is a virtualbeam that is formed by having various radiated waves of each radiatingelements either be in phase and add together within the beam or be outof phase and cancel each other out or to be partially in phase and topartially reinforce or partially canceling outside of the beam. With nohorizontal or vertical phase delay, a beam is formed broadside to thearray, directly perpendicular to the array face. By having a small phasedelay between adjacent elements across the array, the beam can bepointed in any direction. Dynamic phase array require no physicalmovement to aim the beam as the beam is moved electronically. This canproduce antenna motion fast enough to use a small pencil-beam tosimultaneously track multiple targets while searching for new targetsusing just one radar set. The region that can be addressed by a phasedarray system, either electromagnetic or acoustic systems, is called thefield of view and is defined for an antenna's radiating elements as thebeam width of the individual radiating elements in the array and for theantenna's receiving elements as the region for which a signal from atarget or object of interest can be received by the antenna's receivers.By having multiple radiating elements radiating with a controlled phasedelay in adjacent radiating elements, a beam is formed and its beamwidth is directly dependent on the number of radiating elements in theline array or the area array.

The linear phased array, a one dimension line array with equal spacedradiating elements, is easy to analyze and is the basis for analyzingmost two dimension array designs. FIG. 1A shows a prior art schematic ofa linear phased array antenna 10 with eight isotropic radiating elements12 that receive the phased output signals from the eight input/outputphase control elements 14 with a broadside wave pattern and with anangled wave pattern. The input feed array 16 splits the input signalcoming from the array input line 18 in stages to feed each of the eightinput/output phase control elements 14. By changing the phase ofexcitation to each element, the direction of the reinforced beamradiated by the array can be immediately changed. In FIG. 1A, the phasedifferences between adjacent radiators is 0° and the resulting eightradiated waves 20 are in phase and wavefront 22 is broad side to thearray face forming a beam 24 that is perpendicular to the antenna face.

FIG. 1B depicts the same prior art antenna as FIG. 1A but there is aphase delay between each adjacent radiating element 14. The phase delaybetween adjacent elements is Δφ with the left element phase delay at 0°,the next element has a phase delay of Δφ, each element has a delay Δφfrom its left adjacent element and the right most element has a phasedelay of 7 Δφ from the left most element. Each of the eight radiatedwaves 26 is phase delayed from its adjacent wave by Δφ. This causes theresulting wavefront 28 to be propagated at an angle of θ from broadside. The direction of the radiated beam 30 is determined by the elementto element phase delay of Δφ. A larger Δφ moves the beam further off ofbroadside and a phase delay of −Δφ would move the beam to the oppositeside, to the right in FIG. 1B.

The beam width in a phased array antenna is dependent upon the number ofradiating elements on the antenna if all radiating elements are used toform one beam or is dependent upon the number of radiating elements usedto form the beam if only a portion of the array is used. The moreelements used in the array to form the beam, the narrower the beam isand the higher the gain is within the beam width. FIGS. 2A through 2Fdepict the gain plots of prior art linear antenna arrays, each havingdiffering number of isotropic radiating elements, from 1 radiatingelement to 40 radiating elements. In these examples, there is no phasedelay between the radiating elements causing the beam to be broadside tothe array. FIG. 2A depicts the gain plot for a single ideal isotropicradiating element. It has a uniform gain of 0 dB over a range of +/−90°making its field of view +/−90°. FIG. 2B depicts the gain plot for alinear antenna array with three isotropic radiating elements. It has awide beam width of about +/−30° and has an antenna gain of about 5 dB.FIG. 2C depicts the gain plot for a linear antenna array with sixisotropic radiating elements. It has a beam width about +/−10° and anantenna gain of about 8 dB. FIG. 2D depicts the gain plot for a linearantenna array with ten isotropic radiating elements. It has a beam widthabout +/−5° and an antenna gain of 10 dB. FIG. 2E depicts the gain plotfor a linear antenna array with twenty isotropic radiating elements. Ithas a beam width about +/−3° and an antenna gain of 13 d. FIG. 2Fdepicts the gain plot for a linear antenna array with forty isotropicradiating elements. It has a beam width about +/−1.5° and an antennagain of 16 dB. It should be noted that although the beam widths for linearrays of FIGS. 2B through 2F vary from +/−30° for FIG. 2B to +/−1.5°for FIG. 2F, the field of view for all of these is +/−90° and isdetermined by the field of view of the individual radiating elements asdepicted in FIG. 2A.¹

A two dimensional array of radiating elements forms beams in twodimensions, horizontal and vertical. An antenna with an array of 1600radiating elements in a 40 by 40 array would have horizontal beam widthof about 3° and a vertical beam width of about 3°. It would have a gainof 32 dB. Although the beam widths of each of these examples getsnarrower as the number of elements is increased, the field of view ofeach of these is constant and equal to that of each isotropic radiatingelement that make up the array, typically +/−60° to +/−90° bothhorizontally and vertically.

For a phased array antenna, the gain is simply the sum of the number ofelements in the linear or area array, assuming the array is uniformlyilluminated and the aperture is lossless. Therefore ignoring losses, a10 element array would have a gain of 10 or 10 dB, a 100 element arrayhas a gain of 100 or 20 dB and a 1000 element array has a gain of 1000or 30 dB. To get the full gain of a phased array antenna, all of theelements of the array must be used. If half of the elements are used inone beam, that beam would have a gain of half of the full array gain, or3 dB less.

Although it is often ignored in looking a phased array radars and otherphased array systems, the bulk of the radiated power from each elementin the array and for the antenna as a whole is not in the formed beam,but in the areas or directions outside of the beam where most of theindividual waves emitted from each radiating element are out of phasefrom each other and have their signals fully or mostly canceled out.When the radiated wave from two elements are 180° out of phase at aspecific point in the non-remote field or in the remote field of theantenna, they cancel each other out. There is still energy beingradiated from each element in those directions but there is nodetectable signal. A 10 element linear array would have a 10 dB gain anda 10° beam width, with approximately 8% of the radiated energy withinthe beam width and 92% outside. In a similar way, a 20 element lineararray would have a 13 dB gain and about a 6° beam width, withapproximately 5% of the radiated energy within the beam width and 95%outside. Further, a two-dimensional array with 100 elements in a 10×10array, would have a gain of 20 dB and a beam width of 10° in both thehorizontal and vertical planes with less than 1% of the radiated energywithin the beam width and 99% outside. In essence, every phased arrayemits most of its radiated power in non-productive directions, outsideof the formed beam and with most of that radiated energy generallycanceled out or forming complicating side lobes.

A key aspect of radar systems is that the power density of the radartransmitted signal decreases by the square of the distance, i.e. if thepower density of the radiated wave at a range R is P1 watts per unitarea, then the power density at a range of 2R is one fourth of P1 wattsper unit area. The second key aspect is that the return signal from theobject (target) has the same range to power density factor meaning thatthe power density of a return signal at a range of 2R from the object isone fourth of the power density at R from the object. That means that asthe range increases by a factor of 2, the returned signal will bereduced by a factor of 2⁴ or 16 to 1. This is best seen in the basicradar range equations below.

Basic Radar Range Equation:²

P_(r) = received  power$P_{r} = \frac{P_{t}G_{t}G_{r}}{\lambda^{2}\sigma}$R_(ma x) = maximum  antenna  range  for  detection$R_{{ma}\; x} = \sqrt[4]{\frac{P_{t}G_{t}G_{r}\lambda^{2}\sigma}{( {4\pi} )^{3}P_{\min}}}$P_(t) = peak  power[W] G_(t) = gain  of  transmit  antenna  (unitless)G_(r) = gain  of  receive  antenna  (unitless)λ = carrier  wavelength[m]σ = mean  Radar  Cross-Section  (RCS)  of  target[m²]R = range  from  radar  to  target[m]

The maximum range (R_(max)) of a phased array antenna system is themaximum distance where a return signal from an object can be detectedutilizing the full power of the antenna on transmission and all of thereceiving elements on detecting the return signal, i.e. using allelements of the array. This means that to double R_(max), while keepingthe receive sensitivity constant, the beam power must be increased by afactor of 16 by increasing the radiated power per element and/orincreasing the number of radiating elements. Alternatively, the numberof radiating elements and the number of receiving elements in the arraycan both be increased by a factor of 4. These options for increasing theR_(max) of an antenna by a factor of 2 are not only prohibitively costlybut may be physically impossible. Another way to increase power in thebeam to increase R_(max) would be to have radiating elements in thearray that are non-isotropic such as elements that have a narrowed fieldof view due to the use of lenses, horns, parabolics or other means.These can increase power density in the beam by factors of 10×, 100× ormore and increase R_(max) but at the cost of limiting the horizontaland/or vertical field of view of the antenna. To be useful, an antennawith fixed antenna beamforming would have to be moveable to be able toaim the beam from one region of interest to another which defeats thekey advantage of a phased array antenna, instantaneous movement of thebeam to any point in the targeted region.

To fully understand the limitations of current prior art phased arrayantenna systems, a number of example systems will be examined and thesewill be followed up with examples of these same systems afterembodiments of this invention are applied to the systems.

One key application area for phased array radar systems is a ship boardsearch and track phased array radar systems. A complete ship board radarsystem would typically have four phased array antennas, one for each offour directions based on the orientation of the ship (fore, aft,starboard and port). For each of the four antennas, the non-remote fieldregions do not need the full array of radiating elements to detect atarget object such as a plane or surface ship or a missile fired fromeither. In general, surface ship radar systems only need to detecttargets up to 15 km in altitude and only a small portion of the arrayelements are need for the non-remote field. It should be noted that incertain ballistic missile defense situations, a shipboard phased arrayradar system could be required to search and tract targets above 15 km.Ship board phased array radar systems can simultaneously form multiplebeams from one array, by independently controlling multiple portions ofthe array to send radar beams into different directions at the same timeto tract multiple targets in the non-remote field and/or to search andtrack at the same time. The peak radiated power of an antenna requiresall radiating elements are used to transmit a radar wave and allreceiving elements are used to detect a returned radar signal. Peakpower is only needed for remote field target objects with minimum radarcross-sections that are near, at or beyond the radar system's R_(max).Example A is a typical prior art phased array radar antenna system.

Example A: Typical Prior Art Phased Array Radar Antenna

-   -   1000 radiating elements    -   30 dB radiating antenna gain    -   1000 receiving elements    -   30 dB receiving antenna gain    -   R_(max1)=150 km    -   P_(min1)=Power Density at R_(max1)    -   Max Altitude: 15 km    -   Max Elevation Angle (θ₁): 100° (10° past vertical)    -   Min Elevation Angle(θ₂): 0°    -   Max Azimuth Angle: 60°    -   Min Azimuth Angle: −60°

FIGS. 3A and 3B depict antenna gain plots for the prior art 1000isotropic element, phased array radar antenna from Example A. FIG. 3Adepicts the horizontal gain plot 30 for the antenna. The horizontal 3 dBnodes are about at +/−60° with maximum gain of 30 dB. FIG. 3B depictsthe vertical gain plot 32 for the antenna. The 3 dB node is about at100° (10° past vertical) with the same maximum gain of 30 dB. FIG. 4depicts the range chart for the 1000 isotropic element phased arrayantenna of Example A. It has a maximum detection range (R_(max1)) of 150km. The maximum altitude that needs to be targeted is 15 km. The maximumangle of elevation at R_(max1) for the targeted maximum altitude of 15km is 6°. Shaded area 36 denotes a vertical section of the full range ofthe antenna where it can fully detect a target based on its full gain.It should be noted that it covers altitudes of up to 150 km at anglesnear vertical, even though in this application it is assumed that thereare no targets of interest above 15 km. The 1000 isotropic radiatingelements with an antenna gain of 30 dB are used to detect and trackobjects within 150 km with an elevation of 0° to 100° (10° pastvertical) and an azimuth of +60° to −60° from antenna broadside. Thetotal antenna gain including transmission and reception would thus be 60dB.

Another example of a prior art phased array system is for an automotivedriver assist radar system. Radar is used in a motor vehicles as part ofits advanced drive assist system (ADAS) providing a variety of driveraids including collision avoidance, blind spot detection, lane changeassist, pedestrian warning and parking assist. The main collisionavoidance system needs to scan both non-remote fields with a wide fieldof view and a remote field with a narrower field of view. The latestprior art collision avoidance radar systems have phased array systemswith separate antenna radiating element arrays for the non-remote fieldand the remote field and another set of elements for signal reception.³

Example B is a prior art automotive radar system that is part of adriver assist system. FIG. 5 depicts a schematic of the ContinentalEngineering Services ARS 408-21 radar sensor that is an automotivephased array radar with a non-remote field radiating antenna and aremote field radiating antenna and one receiving array.⁴ Themicrophotograph in the upper right portion of FIG. 5 shows the antennasystem face. The antenna has a non-remote field array of transmittingelements seen on the left side of the antenna microphotograph in FIG. 5with a 1×12 array of isotropic radiating elements that operate at 24 GHzand have a gain of about 11 dB. Each radiating element has a field ofview of about +/−60° in azimuth and elevation from the antennabroadside. The 1×12 non-remote field array has no horizontal beamforming, having a horizontal beam width of +/−60°, the same as eachindividual radiating element in the 1×12 array. It has vertical beamforming, having a vertical beam width of 9° targeting an elevation of 0°to 9°. There is no vertical phase control of the elements in thissystem, so the array beam would be broad side and would have a field ofview equal to the beam width covering an elevation of 0° to 9°. Theantenna has a remote field array of transmitting elements, seen in thecenter of the antenna microphotograph in FIG. 5 with a 5×12 array ofisotropic radiating elements operating at 77 GHz and having a gain ofabout 18 dB. It has horizontal beam forming, having a horizontal beamwidth of +/−9° and a vertical beam width of 0° to 9°. There is novertical or horizontal phase control of the elements, so the beam wouldbe broad side and would have a field of view equal to the beam widths,0° to 9° vertically and +/−9° horizontally. The antenna has an array ofreceiving elements, seen in the right side of the antennamicrophotograph in FIG. 5. The receiver array has a 4×12 array ofisotropic receiving elements with a receiver gain of about 17. The arrayforms receiving beam with a width of 9° vertically and 20° horizontally.The four columns of the 4×12 receiver array each have horizontal phasecontrol that can sweep the receiver beam across its horizontal field ofview of +/−60° from antenna broadside. As with the transmittingelements, there is no phase control on the array columns so the receivebeam does not sweep vertically.

FIG. 6 depicts the range plots for the non-remote field antenna rangeplot (dark gray) and remote field antenna range plot (light gray) forthe two transmit arrays and the one receiving array of FIG. 5. Theremote field 5×12 array has a gain of about 18 dB and a beam width of+/−9° at a range of 150 m and +/−4° at a range of 250 m. The non-remotefield 1×12 array has a gain of about 11 dB and a beam width of +/−60°and a range of 10 to 70 m (varies by the angle). The right side 4×12array of omnidirectional receiving elements and is used for both thenon-remote field and the remote field. The remote field radiated wavehas only 15% of its radiated power within the +/−9° beam width up to 150m and only 7% of its radiated power within the +/−4° beam width up from150 to 250 m. Fully 93% of the antenna's radiated power is not in theremote field beam and is therefore is not used in detecting remote fieldobjects. All of the radiating elements of the non-remote field and theremote field transmitting arrays are isotropic and all of the receivingelements of the receiving array are omnidirectional.

Another electromagnetic phased array antenna system is an antenna forthe transmission and/or reception of communication signals. One uniquephased array communication system is the base station used in cellularphone communication systems. In typical cellular phone base stations, asystem of line array phased array antenna are used to transmitelectromagnetic communication signals to mobile receivers and to receiveelectromagnetic communication signals form mobile transmitters. A priorart example of a typical base station tower of is Example C. There arethree sets of transmitting line arrays and three sets of receiving linearrays, each set covering 120° of azimuth, covering 360° in total. Eachset would have at least one receiving line array and at least onetransmitting line array. For Example C we will look at one base stationradiating line array. Each line array will have eight receiving ortransmitting elements arranged in a vertical line with a spacing fixedby the frequency or frequencies used. As depicted in FIG. 7, line arraytransmitting antenna 200 has eight isotropic radiating elements 202located on the face 204 of the antenna. Each element would have a gainof 1 dB and would have a field of view +/−60° in azimuth and +/−60° inelevation. The eight element line array would have a beam width of atleast 120° horizontally and about +/−10° in elevation. Because a basestation transmit antenna must always be able to send signals to mobilereceivers in any azimuth or elevation within the array field of view,phase control is not used to move or steer the transmitted beam.

The same requirement applies to the receiver line arrays that must beable to receive transmitted signals from any mobile transmitter withinthe array's field of view. FIGS. 8A and 8B depict the azimuth gain plot206 and elevation gain plot 208 for the eight transmitting elementphased array line antenna of FIG. 7 with a maximum gain of 9 dB. If weassume that the eight transmitting element line array has a verticalbeam width of 20°, then only 17% of the radiated energy of thetransmitting element line array would be in the transmitted beam and 83%would be in other directions and would not be utilized. In addition, inthe antenna remote field, only a narrow portion of the 20° vertical beamwidth is at an altitude that would have mobile transceivers. In theremote field, only 5% to 10% of the radiated signal is useful, with 90%or more not utilized.

Acoustic Phased Array Antenna Systems

Another key application area for phased array antenna systems isacoustic phased arrays such as sonar and ultrasound. In medical andindustrial ultrasound acoustic imaging, a line array or an area array oftransducer elements are used to transmit an ultrasonic wave into atarget body or object and then to receive back a reflected ultrasonicacoustic wave from objects within the body or object. Sonar acousticphased array antenna systems come in two main forms. One is a sonarsystem where acoustic signals are transmitted out by an array oftransducers and where the same array of transducers receive thereflected signals. The other sonar system is a passive sonar where noacoustic wave is transmitted and the sonar system simply listens foracoustic signals generated by an object of interest, such as a sonartowed array system listening for surface ships, submarines andtorpedoes. As in radar phased array systems, acoustic phased arraysystems use multiple transmitting elements such as transducers, alignedin a line array or an area array to form a beam of in phase acousticwaves and to receive reflected acoustic signals. Changing the phasebetween adjacent acoustic elements changes the direction, in azimuth andelevation, of a transmitted beam of reinforcement in the radiatedacoustic waves. This creates radiated beams in any desired directionwithin the field of view of the acoustic antenna. The same phase controlis used on each receiving element the do the same beamforming on thereceived signals, reinforcing the signals from the selected directionand canceling out the signals from other directions. In sonar phasedarray antenna applications, the transmitting elements need to besufficiently isotropic to cover +/−60° to +/−90° in azimuth and +/−45°to +/−90° in elevation. Unlike surface ship radar, sonar systems onsubmerged platforms, i.e. submarines, must have a field of view thatgoes above and below 0° elevation. FIG. 9A depicts functional diagram ofan active sonar system and FIG. 9B depicts active beamforming, bothhaving a cylindrical transducer array.⁵ A focused transmitting elementsuch as an acoustic transducer with a focusing lens would narrow thefield of view by a factor of X and increase the power density in thebeam by the same factor, X. Most sonar acoustic array systems rely onphase control of each transducer for beamforming such as detailed inUS6842401B2, Chiang et al. The use of one large acoustic lens to focus areturning acoustic signal was described in US4065748A, Maguer, et al.

Example D is a prior art sonar phased array with 400 isotropictransducers and a transmitting gain of 26 dB. It has a field of view of+/−60° in azimuth and +/−60° in elevation. In this example, the sonararray has an R_(max) of 150 km when using all 400 elements to form onebeam of in phase acoustic waves. The receiving gain of this sonar phasedarray system would be 26 dB (based upon its 400 receiving elements). Thetotal sonar antenna gain would be the combined antenna transmit andreceive gain or 52 dB (26 dB transmit gain and 26 dB receive gain). Theprior art transducer array of Example D is acoustic equivalent of theradar antenna array in Example A. As with a radar array with 400elements, the sonar array with 400 elements arranged in a 20 by 20array, would have a beam width of 6° in azimuth and elevation. With thefield of view for the array at +/−60° in azimuth and elevation, lessthan 1% of the emitted acoustic power of the array is within the beamand more than 99% is outside of the beam and not useful. It should benoted that acoustic signals can have significant signal loss due toattenuation particularly in water and in high liquid medium such asmuscle, fat and other portions of body. For this specification, theattenuation due to acoustic absorption is ignored for simplicity.

Another phased array acoustic system with an array of isotropic elementsis a towed array. A towed array is a system of hydrophones towed behinda submarine or surface ship on a long cable that can be kilometers long.Most towed array systems are passive and do not emit any acoustic signalbut just receives acoustic signals emanating from distant object such asa submarine, a surface ship or a torpedo or even a whale. Although thereare towed array that are active such as the Atlas Elektronik ACTASsystem, we will focus on passive towed array systems. The array'shydrophones can be used to detect sounds and with beamforming and signalprocessing, identify a target's direction and range and with signalanalysis identify if the target is a ship, a submarine or a whale andeven identify the type of ship by its distinctive acoustic signature.Each towed array system has a specific passive frequency range such as50 Hz to 1600 Hz. Longer towed array systems may have 100's or 1000's ofacoustic sensing elements and amplifiers. Most towed array systems useceramic piezoelectric transducers for sensing.

Essentially, a towed array acoustic system is a linear phased arraysystem. Transducer elements in the towed array are omnidirectional,typically receiving acoustic signals over a vertical range of +90° to−90° and over a horizontal range of +90° to −90°. The towed array systemhas R_(max) that varies based on the signal strength of the distanttarget. Example E is a prior art passive towed array system with 1000omnidirectional transducers used only for sensing. It has an antennagain of 30 dB. It can detect an emitted acoustic signal of strength X ata range of R_(max4).

Optical Phased Array Systems

An optical phased array (OPA) system involves the controlling of thephase of light waves transmitted from and/or received at atwo-dimensional phased array antenna. It is the optical analog of aphased array radar and like a phased array radar, has no moving parts.Two types of OPA systems in use today in automotive systems are Lidar(light detection and ranging) and Ladar (laser detection and ranging).Ladar systems are more versatile than radar systems in part because ofthe shorter wavelength associated with laser beam transmissions. Phasedarray optics (PAO) can be arrays of lasers or spatial light modulators(SLM) with addressable phase and amplitude elements. Two-dimensionaloptical phase array were described in US8988754 B2, Sun et al, and inUS9753351, Eldada, each having only one lens covering the whole array.

FIGS. 10A through 10C depict three examples of an eight emittingelement, optical phased array with three differing wavefronts. Theoptical phased array of FIG. 10A is timed with no phased delay betweenelements so the combined waves from each emitting element form acomposite wave radiating directly perpendicular (broadside) to thearray. The optical phased array of FIG. 10B is timed with phase delaysbetween each element to have the combined waves from each emittingelement form a composite wave radiating an angle off center. The opticalphased array of FIG. 10C is timed with phase delays between each elementsuch that the combined waves from each emitting element form a compositewave radiating wavefront appearing to emanate from a point source behindthe array.⁶ As with a radar phased array, by adjusting the phase of thevarious elements, a wavefront can be sent in a beam in any directionfrom at least +/−60° to +/−90° horizonally and +/−60° to +/−90°vertically.

FIGS. 11A through 11C depict optical linear phased arrays and theiremitted wave patterns. Each optical phased array has a laser feeding anarray of emitters. As with phased array radar and acoustic antennasystems, optical phase array antennas can control of the output of eachemitter to form a beam of reinforced optical waves in any desireddirection. FIG. 11A depicts an optical linear array with four widelyspaced emitters and the resulting beam and side lobes. FIG. 11B depictsan optical array with four densely spaced emitters and the resultingbeam. FIG. 11C depicts an optical array with eight densely spacedemitters and the resulting beam which with more radiating emittingelements, is narrower than the beam in FIG. 11B.⁷ A typical prior artoptical phased array system is described in Example F. It is an opticalphased array system with 100 isotropic light emitters in an array of 10rows with 10 elements per row. The antenna gain is 20 dB and has a beamwidth of 10° in azimuth and elevation. Its R_(max) is 150 km when usingall 100 elements. With the 10° beam width, less than 1% of the radiatedoptical signal is in the beam width and more than 99% in outside of thebeam and not providing useful function.

Problem to be Solved

In any phased array antenna system, there is a requirement that a beamformed by individually changing the phase of each radiating element canbe electronically steered over the required azimuth sweep and elevation.Most phased array radar antenna contain 100's to 1000's of isotropicradiating elements that over a broad range of horizontal and verticalangles from the antenna broad side have uniform radiating gain plots atleast over a horizontal range of +/−60° and over a vertical range of atleast 0° to 90° for ship board or ground based systems and a verticalrange of at least +/−60° to for airborne, projectile or space basedsystems. Generally, the radiated wave power over this whole space needsto be uniform within 3 dB. For ground based or surface ship antennasystems that need to have a field of view of 360° would require fourantenna arrays, each facing 90° off from the next, covering 360° witheach overlapping the next adjacent antenna by 30°. Vertically, eachantenna face covers a little more than 100° and thus each antenna faceproviding a 20° overlap with their adjacent antenna faces. In manyground based or ship board phased array radar systems, the maximumaltitude of interest is the maximum altitude for which a target ofinterest could achieve. In the case of aircrafts, that would be about50,000 feet or less than 10 miles or about 15 km. A phased array antennasystem with an R_(max) of 150 km or more, would hit maximum altitude at6° elevation. At all range values of less than 0.84 R_(max), the antennasystem has excess gain. It would be beneficial if the excess radar powerthat is transmitted in the non-remote field directions could be tradedoff to increase the gain the remote field to increase R_(max).

As noted above, the bulk of the radiated power from each element in thearray and for the antenna as a whole is not in the formed beam, but inthe areas or directions outside of the beam where the transmitted wavesfrom each of the multiple radiating elements are fully or partially outof phase from each other and have their signals fully or mostly canceledout. When the radiated wave from two elements are 180° out of phase in aspecific point in the non-remote field or remote field of the antenna,they cancel each other out. There is still energy being radiated fromeach element in all directions covered by each element's field of view,typically +/−60° in azimuth and 0° to 90° in elevation. A 10 elementlinear array would have a 10 dB gain and a 10° beam width, withapproximately 8% of the radiated energy within the beam width and 92%outside. In a similar way, a 20 element linear array would have a 13 dBgain and about a 6° beam width, with approximately 5% of the radiatedenergy within the beam width and 95% outside. Further, in atwo-dimensional array with 100 elements in a 10×10 array, would have again of 20 dB and a beam width of 10° in both the horizontal andvertical planes with approximately 1% of the radiated energy within thebeam width and 99% outside. In essence, every phased array emits most ofits radiated power in non-productive directions, outside of the formedbeam and with most of that radiated energy generally canceled out orforming complicating side lobes.

It is desirable that the excess radiated power targeting non-remotefield regions of phased array antenna systems be utilized to increaseradiated power targeting remote field regions to extend the maximumrange of the antenna system without increasing the number of radiatingelements nor the radiated power per element.

BRIEF DESCRIPTION OF THE INVENTION

The invention provides a phased array antenna system that has the fullcapability of multiple beam formation, beam direction and elevationagility and transmit and receive capability as a standard phased arrayantenna system but that can offer an increase of 50% or more in maximumrange (R_(max)) with the same number of radiating elements and the sameradiated output power per element. The invention utilizes some of theexcess power used to target non-remote field objects and utilizes it toextend the R_(max) in the remote field of the phased array system. Asnoted above, the non-remote field is defined as the range the antenna to0.84 R_(max) and the remote field is defined as the range beyond 0.84R_(max).

Therefore, according to one embodiment of the invention, a phased arrayradar antenna comprises a plurality of generally isotropic radiatingelements targeting the detection and/or tracking of objects in thenon-remote field and a plurality of non-isotropic radiating elementstargeting the detection and/or tracking of objects in the remote field.

According to another embodiment of the invention, a phased array radarantenna comprises a plurality of generally omnidirectional sensingelements targeting the detection and/or tracking of objects in thenon-remote field and a plurality of non-omnidirectional sensing elementstargeting the detection and/or tracking of objects in the remote field.

According to another embodiment of the invention, a phased arrayacoustic antenna comprises a plurality of generally isotropic radiatingelements targeting the detection and/or tracking of objects in thenon-remote field and a plurality of non-isotropic radiating elementstargeting the detection and/or tracking of objects in the remote field.

According to another embodiment of the invention, a phased arrayacoustic antenna comprises a plurality of generally omnidirectionalsensing elements targeting the detection and/or tracking of objects inthe non-remote field and a plurality of non-omnidirectional elementstargeting the detection and/or tracking of objects in the remote field.

According to yet another embodiment of the invention, an optical phasedarray system comprises a plurality of generally omnidirectional sensingelements targeting the detection of objects in the non-remote field anda plurality of non-omnidirectional sensing elements targeting thedetection of objects in the remote field.

According to further embodiment of the invention, an optical phasedarray system comprises a plurality of generally isotropic emittingelements for the transmission of communication signals in the non-remotefield and a plurality of non-isotropic emitting elements for thetransmission of communication signals in the remote field.

According to another embodiment of the invention, an optical phasedarray system comprises a plurality of generally omnidirectional sensingelements for the reception of communication signals in the non-remotefield and a plurality of non-omnidirectional sensing elements for thereception of communication signals from the remote field.

According to one additional embodiment of the invention, a phased arraymicrowave antenna comprises a plurality of generally isotropic radiatingelements for the transmission of communication signals in the non-remotefield and a plurality of non-isotropic radiating elements for thetransmission of communication signals in the remote field.

According to one further additional embodiment of the invention, aphased array microwave antenna comprises a plurality of generallyomnidirectional receiving elements for the reception of communicationsignals from the non-remote field and a plurality of non-isotropicreceiving elements for the reception of communication signals from theremote field.

According to another embodiment of the invention, a phased array antennacomprises a first plurality of generally isotropic radiating elementsused to form radiating beams in the non-remote field and a secondplurality of generally isotropic radiating elements each radiatingthrough focusing lenses for forming non-isotropic radiating waves.

According to another further embodiment of the invention, a phased arrayantenna comprises a first plurality of generally isotropic radiatingelements used to form radiating beams in the non-remote field and asecond plurality of generally isotropic radiating elements eachradiating through horn structures to redirect the isotropic radiatedwaves into non-isotropic radiating waves.

According to a yet further embodiment of this invention, a phased arrayantenna comprises a first plurality of radiating elements having aradiating pattern with a first field of view in the horizontal plane anda second field of view in the vertical plane and a second plurality ofradiating elements having a radiating pattern with a third field of viewin the horizontal plane and a fourth field of view in the vertical planeand wherein the third field of view is more than 2:1 narrower than thefirst field of view and/or the fourth field of view is more than 2:1narrower than the second field of view.

According to another embodiment of this invention, a phased arrayantenna comprises a plurality of radiating elements having a generallyisotropic radiating pattern and having focusing elements in the wavepath of each isotopic radiating element that focus the radiated waves inthe vertical plane to form a beam width with a narrower field of viewand an increased power density within the beam width.

According to yet another embodiment of this invention, a phased arrayantenna comprises a plurality of receiving elements having a generallyomnidirectional field of view and having focusing elements in the wavepath of each receiver to focus received waves in the vertical plane andincrease the power density of the return signal at the receivingelements.

According to an embodiment of this invention an algorithm for utilizingembodiments of this invention comprises an analysis software tool thatidentifies whether a remote or non-remote field of view is to beaddresses in performing an operation of the phased array antenna systemof any of the embodiments of this invention and directs the system toutilize the correct portion of the elements of the antenna to bestaddress those regions. Specifically, the algorithm would directnon-remote regions to be addresses to those portions of the antenna withisotropic radiating elements and/or omnidirectional receiving elementsand would direct remote regions to be addresses to those portions of theantenna with non-isotropic radiating elements and/or non-omnidirectionalreceiving elements.

For the purposes of this specification, a generally isotropic radiatingelement is defined as one that has a radiated wave that has a field ofview of at least +/−60° in azimuth and at least 0° to 90° verticallyfrom antenna broadside. Also, a non-isotropic radiating element isdefined as one that has a radiated wave that has a field of view atleast 50% narrower than the field of view of the generally isotropicradiating elements of the same antenna in the horizontal and/or verticalplanes. An omnidirectional receiving element is defined as one that hasan angle of reception of signals of at least +/−60° horizontally and atleast 0° to 90° vertically from antenna broadside. Also, anon-omnidirectional receiving element is defined as one that has anangle of reception at least 50% narrower than the angle of reception ofthe generally omnidirectional receiving elements of the same antenna inthe horizontal and/or vertical planes.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate embodiments presently contemplated for carryingout the invention.

In the drawings:

FIGS. 1A and 1B depict schematics of a prior art linear array of eightradiating elements with and without phase delays and its wavefrontpatterns.

FIGS. 2A through 2F depict antenna gain plots for prior art line arrayswith varying numbers of isotropic radiating elements.

FIGS. 3A and 3B depict the azimuth and elevation antenna gain plots fora prior art array of 1000 isotropic radiating element, phased arrayradar antenna system.

FIG. 4 depicts the range plot for prior art array of 1000 isotropicradiating element, phased array radar antenna system.

FIG. 5 depicts a schematic of a prior art automotive driver assist radarsystem.

FIG. 6 depicts the non-remote field and remote field range plots of theautomotive driver assist radar system of FIG. 5.

FIG. 7 depicts a prior art cellular tower linear array.

FIGS. 8A and 8B depict the azimuth and elevation antenna gain plots ofthe prior art cellular tower linear array of FIG. 7.

FIGS. 9A and 9B depict a schematic of a prior art sonar array system andits radiated beam.

FIGS. 10A through 10C depict a prior art line array of eight isotropicoptical radiating elements and three of its radiating wavefronts.

FIGS. 11A through 11C depict radiating elements and resulting beam formsof a prior art optical phased array.

FIGS. 12A and 12B depict the azimuth and elevation antenna gain plotsfor a 500 isotropic radiating element antenna system according to anembodiment of this invention.

FIG. 13 depicts the range chart of a 500 isotropic radiating elementantenna system according to an embodiment of this invention.

FIGS. 14A and 14B depict the azimuth and elevation antenna gain plots ofa 500 non-isotropic radiating element array in an antenna systemaccording to an embodiment of this invention.

FIG. 15 depicts the range chart of a 500 non-isotropic radiating elementarray in an antenna system according to an embodiment of this invention.

FIGS. 16A and 16B depict the azimuth and elevation antenna gain plots ofa 1000 radiating element antenna system that contains a 500 isotropicradiating element array and a 500 non-isotropic radiating element arrayin one antenna system according to an embodiment of this invention.

FIG. 17 depicts the range chart of a 1000 radiating element antennasystem that contains a 500 isotropic radiating element array and a 500non-isotropic radiating element array in one antenna system according toan embodiment of this invention.

FIGS. 18A and 18B depict the azimuth and elevation antenna gain plotsfor a cellular tower line array with all non-isotropic radiatingelements according to an embodiment of this invention.

FIGS. 19A through 19C depict a perspective view, a verticalcross-section and a horizontal cross-section of a cylindrical conductivelens mounted over an isotropic radiating element that forms anon-isotropic radiating wave according to an embodiment of thisinvention.

FIGS. 20A through 20C depict a perspective view, a verticalcross-section and a horizontal cross-section of a cylindrical dielectriclens mounted over an isotropic radiating element that forms anon-isotropic radiating wave according to an embodiment of thisinvention.

FIGS. 21A through 21C depict a perspective view, a verticalcross-section and a horizontal cross-section of another cylindricaldielectric lens mounted over an isotropic radiating elements that formsa non-isotropic radiating wave according to an embodiment of thisinvention.

FIGS. 22A and 22B depict two phased array antennas containingcylindrical lenses each covering either a number of isotropic radiatingelements in a horizontal row or covering all of the isotropic radiatingelements in a horizontal row according to an embodiment of thisinvention.

FIGS. 23A through 23D depict prior art microwave E-field and H-fieldhorns that form a narrow beam width horizontally and verticallyrespectively and the horizontal and vertical gain plots for the priorart H-field horn.

FIGS. 24A through 24C depict the front view, horizontal cross-sectionand vertical cross-section of a segment of a radiating antenna wheremicrowave reflective sidewalls are formed in situ to form an array ofH-field horns according to an embodiment of this invention.

FIG. 25 depicts cellular tower line array with cylindrical lensesmounted over each isotropic radiating element forming non-isotropicradiating elements according to an embodiment of this invention.

FIGS. 26A through 26E depict a processing sequence for formingcylindrical lenses in situ over the radiating surface of a phased arrayantenna according to an embodiment of this invention.

FIG. 27 depicts a vertical cross-section of a portion of an opticalphased array with cylindrical lenses formed over the radiating elementsaccording to an embodiment of this invention.

FIG. 28 depicts a vertical cross-section of a portion of another opticalphased array with cylindrical lenses formed over the radiating elementsaccording to an embodiment of this invention.

FIG. 29 depicts a vertical cross-section of a portion of an opticalphased array with cylindrical lenses formed over the radiating elementsaccording to an embodiment of this invention.

FIG. 30 depicts a vertical cross-section of a portion of another opticalphased array with cylindrical lenses formed over the radiating elementsaccording to an embodiment of this invention.

FIGS. 31A and 31B depict vertical cross-sections of conductive anddielectric cylindrical lenses that are offset from the face of theantenna according to an embodiment of this invention.

FIGS. 32A through 32C depict a perspective view, a verticalcross-section and a horizontal cross-section of a cylindrical lenssimilar to the lens in FIG. 20 except that the lens has reducedcurvature and reduced beamforming.

FIGS. 33A through 33C depict a perspective view, a verticalcross-section and a horizontal cross-section of an oval lens similarthat does beam forming in both the vertical and horizontal plane.

FIG. 34 depicts a phased array radar antenna with a plurality ofisotropic radiating elements and with a plurality of non-isotropicradiating elements according to an embodiment of this invention.

FIG. 35 depicts a phased array acoustic antenna with a plurality ofisotropic radiating elements and with a plurality of non-isotropicradiating elements according to an embodiment of this invention.

DETAILED DESCRIPTION

Embodiments of the invention apply to phased array antenna systems forelectromagnetic radiating elements and acoustic radiating elements. Tobetter understand the invention and how embodiments could be applied toa typical phased array antenna systems, we will look at modifying theprior art phased array antenna systems of examples detailed above.

The antenna in Example A has 1000 isotropic radiating elements with again of 30 dB and an R_(max1) of 150 km. Example G is a phased arrayradar antenna with a combination of isotropic radiating elements andnon-isotropic radiating elements according to an embodiment of thisinvention. It has the same number of radiating elements as in Example A,1000 elements, with the same radiated output power per element. It has500 isotropic radiating elements and 500 non-isotropic radiatingelements. The 500 isotropic radiating elements would be dedicated toshorter range target detection and tracking (non-remote field) with afull field of view of 0° to 100° in elevation (from the ground to 10°past vertical) and −60° to +60° in azimuth (same as the isotropicradiating elements in Example A). The 500 non-isotropic radiatingelements would be dedicated to long range target detection (remotefield) with a reduced field of view of 0° to 6° in elevation (only onetwentieth of the vertical field of view as the isotropic radiatingelements) while maintaining a field of view of −60° to +60° in azimuth.

FIGS. 12 and 12B depict the antenna gain plots for the 500 isotropicradiating elements of the non-remote field portion of the phased arrayof Example G according to an embodiment of this invention. FIG. 12Adepicts the horizontal gain plot 210 for the 500 isotropic radiatingelements. The horizontal gain plot 30 for the 1000 isotropic radiatingelements of Example A is overlaid for comparison. This antenna portionhas half as many radiating elements, one half the power level. Themaximum antenna gain is 27 dB, 3 dB less than the 1000 isotropicradiating element antenna in Example A. The 3 dB horizontal nodes areabout at +/−60° from the antenna broadside. FIG. 12B depicts thevertical gain plot 212 for the 500 isotropic radiating elements ofExample G as well as the vertical gain plot 32 for the 1000 isotropicradiating elements of Example A. It has its 3 dB vertical nodes at aboutat 100° (10° past vertical) and at 0° as in Example A with maximum gainof 27 dB, 3 dB less than in Example A.

FIG. 13 depicts the range chart 214 for the 500 isotropic elementsportion of the phased array antenna of Example G which has a maximumdetection range (R_(max2)) of 126 km (0.84% of R_(max1) of Example A).The range chart 34 for the 1000 isotropic elements of Example A isincluded for comparison. The targeted maximum altitude is 15 km as inExample A. Shaded area 216 denotes a vertical cross-section of the fullrange of the 500 isotropic elements portion of the antenna where it canfully detect a target based on the gain of the 500 elements. It coversaltitudes of up to 126 km compared to the 150 km altitudes in thebaseline array of Example A. For those few radar applications that needhigher radar coverage above 15 km, such as searching for ballisticmissiles or tracking satellites, the 500 isotropic radiating elements ofExample G provides coverage to altitudes up to 126 km. The 500 isotropicradiating elements are used to detect and track objects within a rangeof 126 km with an elevation of 0° to 100° (10° past vertical) and from+60° to −60° horizontally from antenna broadside. The Example Gspecifications for the 500 isotropic radiating elements covering thenon-remote field are:

Example G: Non-Remote Field Elements

-   -   500 radiating elements    -   27 dB gain    -   R_(max2)=126 km    -   P_(min2)=Power Density at R_(max2)    -   Max Altitude: 15 km    -   Max Vertical angle (θ₁): 100°    -   Min Vertical Angle (θ₂): 0°    -   Max Azimuth Angle: 60°    -   Min Azimuth Angle: −60°

FIGS. 14A and 14B depict the antenna gain plots for the 500non-isotropic radiating elements of the remote field portion of theantenna in Example G according to an embodiment of this invention. FIG.14A depicts the horizontal gain plot 220 for the 500 non-isotropicradiating elements. The antenna gain for the 500 non-isotropic elementsis 27 dB, 3 dB less than the 1000 isotropic radiating elements ofExample A. The non-isotropic radiating elements also has an additionalgain of 13 dB (20X) due to the narrow elevation field of view of 6°versus the full elevation of 120° of the baseline of Example A. The neta gain of 500 non-isotropic radiating elements of the antenna in ExampleG is 40 dB (27 dB antenna gain plus 13 dB gain due to the narrowvertical field of view) with the horizontal 3 dB nodes at about at+/−60°. FIG. 14B depicts the vertical gain plot 222 for the 500non-isotropic radiating elements. It has its 3 dB vertical node at aboutat 6° and at 0° with a maximum gain of 40 dB. It has a 6° vertical fieldof view centered at 3° elevation.

FIG. 15 depicts the range chart 226 for the portion antenna with the 500non-isotropic radiating elements according to an embodiment of thisinvention. Striped area 226 denotes a vertical cross-section of the fullrange of the non-isotropic portion of the antenna where it can fullydetect a target based on the gain of the 500 non-isotropic elements. Ithas a maximum detection range (R_(max3)) of 267 km for the elevationrange of 0° to 6° with its maximum gain of 40 dB. The maximum elevationat R_(max3) for the targeted altitude of 15 km is 6°. The 500non-isotropic radiating elements will detect target objects in theremote field from 126 km to 267 km at altitudes of 0 to 15 km, a 78%increase in R_(max) over the base line antenna in Example A.

Example G: Remote Field Elements

-   -   500 radiating elements    -   40 dB gain (27 dB from 500 elements+13 dB from 6° vertical band        width)    -   R_(max3)=267 km (78% increase in range over Example A)    -   P_(min3)=Power at R_(max3)    -   Max Altitude: 15 km    -   Max Vertical angle (θ₁): 6°    -   Min Vertical Angle (θ₂): 0°    -   Max Azimuth Angle: 60°    -   Min Azimuth Angle: −60°

FIGS. 16A and 16B depict the combined antenna gain plots for the 1000element antenna of Example G with 500 isotropic radiating elements forthe non-remote field and 500 non-isotropic radiating elements for theremote field according to an embodiment of this invention. FIG. 16Adepicts the horizontal gain plot 210 of the 500 isotropic radiatingelements portion of the antenna and horizontal gain plot 220 of the 500non-isotropic radiating elements portions of the antenna in Example Gcombined onto the same plot. The horizontal gain plot of isotropicelements 210 is shown as a dashed line and the horizontal gain plot ofnon-isotropic elements 220 is shown as a dash-dot-dash line. Thehorizontal 3 dB nodes for the isotropic elements are about at +/−60°with maximum gain of 27 dB. The horizontal 3 dB nodes for thenon-isotropic elements are about at +/−60° with maximum gain of 40 dB.FIG. 16B depicts the vertical gain plot 212 for the 500 isotropicradiating elements portion of the antenna and vertical gain plot 220 ofthe 500 non-isotropic radiating elements portions of the antenna inExample G combined onto the same plot. The vertical gain plot 212 of theisotropic elements is shown as a dashed line and the vertical gain plot222 of non-isotropic elements 48 is shown as a dash-dot-dash line Forthe isotropic elements, the 3 dB node is about at 100° (10° pastvertical) with the maximum gain of 27 dB. For the non-isotropicelements, the 3 dB notes are at 0° and 6° and with a maximum gain of 40dB.

FIG. 17 depicts the combined range chart 230 for the Example G antenna.It includes range chart 214 as depicted in FIG. 13 for the 500 isotropicradiating elements portion of the phased array antenna which has amaximum detection range (R_(max2)) of 126 km and range chart 226 asdepicted in FIG. 15 for the 500 non-isotropic radiating elements portionof the phased array antenna which has a maximum detection range(R_(max3)) of 267 km according to an embodiment of this invention.Shaded area 216 denotes a vertical cross-section of the full range ofthe antenna where it can fully detect a target based on the gain of the500 isotropic radiating elements. Diagonal lined area 228 denotes avertical cross-section of the full range of the non-isotropic portion ofthe antenna where it can fully detect a target based on the gain of the500 non-isotropic radiating elements. The targeted maximum altitude istargeted at 15 km. The maximum elevation at R_(max3) for the targetedmaximum altitude of 15 km is 6°. The 500 isotropic radiating elementswill detect targets from 0 km to 126 km at altitudes of 0 to 126 km(well beyond the required 15 km). The 500 non-isotropic radiatingelements will detect target objects from 126 km to 267 km at altitudesof 0 to 15 km. The combination of the 500 isotropic and 500non-isotropic radiating elements covers all targeted areas over a rangeof 0 to 267 km over an altitude of 0 to a minimum of 15 km and a maximumaltitude of 126 km altitude.

In Example G, which has the same 1000 radiating elements and the samelevel of radiated power as in Example A, with 500 isotropic elementsdedicated to the non-remote field and 500 non-isotropic elementsdedicated to the remote field, the maximum range (R_(max)) is increasedfrom 150 km (of baseline Example A) to 267 km, a 78% increase. The 500isotropic radiating elements are used to detect and track objects withinthe non-remote field, out to 126 km with an elevation of 0° to 100° (10°past vertical) and from +60° to −60° horizontally from antennabroadside. The 500 non-isotropic radiating elements are used to detectand track objects in the remote field from 126 km to 267 km with anelevation of 0° to 6° and from +60° to −60° horizontally from antennabroadside. All of the target area covered by the radar antenna of priorart Example A covering out to 150 km distance and up to 15 km altitudeare covered by the 1000 mixed isotropic and non-isotropic radiatingelements of the radar antenna of Example G according to an embodiment ofthis invention and the maximum distance of antenna coverage is pushedout to 267 km.

In order to best utilize the extended range the provided with variousembodiments of this invention, an algorithm for an analysis softwaretool is proposed as an embodiment of this invention. This algorithmwould determine whether a remote or non-remote field of view is to beaddressed in performing an operation of the phased array antenna systemof embodiments of this invention and would direct the system to utilizeeither the isotropic or the non-isotropic elements of the antenna tobest address those regions. Specifically, the algorithm would directnon-remote regions to be addressed by utilizing all or portions of theantenna with isotropic radiating elements and/or omnidirectionalreceiving elements and would direct remote regions to be addresses bythose portions of the antenna with non-isotropic radiating elementsand/or non-omnidirectional receiving elements.

Example H is an automotive phased array radar antenna similar to theautomotive phased array antenna of Example B, but with modificationsbased embodiments of this invention. The automotive radar of Example Bhas all isotropic radiating elements and all omnidirectional receivingelements. In Example H, remote field array of transmitting elements inthe center 5×12 array of transmitting elements (FIG. 3) are modified toform non-isotropic radiating elements. Specifically, each of theseremote field radiating elements would have horizontal beam forming tonarrow radiated beam in the horizontal plane from the original +/−60° ofExample B to +/−9°, the only field of view required in the remote fieldof this automotive application. This would increase the radiated powerdensity in the remote field by a factor 6.7 X and increase gain by morethan 8 dB while covering the same field as the automotive radar ofExample B. The increased gain pushes the maximum range of the antennafrom the baseline 250 m to 400 m.

In another embodiment of this invention, detailed in Example I, theantenna elements of transmitting line arrays and the receiving linearrays of a cellular tower array would have focusing structures in theradiating paths of each transmitting element and each receiving element.Example I is the same cellular tower line array phased array antennasystem as in Example C except the transmitting element are non-isotropicand are focused in the vertical plane to have the radiated wave of eachradiating element restricted to a narrow vertical field of view andwhile maintaining the same wide horizontal field of view. Thetransmitting line array antenna has eight radiating elements located onthe face of the antenna (the same as the prior art antenna of FIG. 7).The narrow transmitted beam width in the vertical plane is 20°, therewould be a 6 X increase in power density within the beam verses that inExample C, or an additional 8 dB gain within the beam width. FIGS. 18Aand 18B depict the azimuth gain plot 340 and elevation gain plot 342 forthe Example I antenna and that is an embodiment of this invention. Theazimuth gain plot 206 from FIG. 8A and elevation gain plot 208 from FIG.8B for the baseline antenna of Example C are included for comparison.The eight transmitting element phased array line antenna of Example Ihas an antenna gain of 9 dB and a focusing gain of 8 dB for a total gainof 17 dB. The maximum range to get a valid signal from the antenna to amobile receiver would be extended by a factor of 2.4 X. This extendedrange is accomplished with the same number of radiating elements andwith the same output power per element as the baseline of Example C.

In a similar way, the receiving line array of a cellular tower wouldhave similar focusing structures as the transmitting line arrays toextend the receiving maximum range by a similar factor of 2.4 X. Thisextension is accomplished using an embodiment of this invention usingthe same number of receiving elements, each with the same level ofsignal detention. Using this embodiment of the invention would permitcellular towers to be spaced more than twice the distance as currentprior art cellular towers, cutting the number of towers and all of theirassociated electronics and hardware by a factor of four.

Although only three examples of electromagnetic phased array antennasystems, a shipboard phased array radar system, an automotive radarsystem and a cellular tower communication antenna system are describedabove, the embodiments of this invention relative to phased arrayelectromagnetic systems equally applies to other phased arrayelectromagnetic systems such as microwave inspection systems and othertypes of phased array electromagnetic systems. Ones skilled in the artcould apply the principles of this invention to many otherelectromagnetic phased array systems.

Non-Isotropic Radiating Elements:

It is clear from the proceeding sections of this specification that theembodiment of this invention detailed in Example G of a phased arrayradar antenna with a plurality of isotropic radiating elements and aplurality of non-isotropic radiating elements provides a 78% increase inmaximum range of the radar system versus the prior art base line systemof Example A without increasing the number of radiating elements norincreasing the radiated power of the elements has clear performanceadvantages over the prior art antenna system of Example A. This sectionof this specification will address how to achieve the proposed narrowedvertical field of view of the 500 non-isotropic radiating elements aswell as the 500 non-omnidirectional receiving elements that targetremote field objects in this embodiment of the invention.

There are well known radiating elements that have narrower verticaland/or horizontal field of views and have corresponding higher powerdensity within the beam as well as receiving elements that havenon-omnidirectional field of views. These include lenses, reflectors andhorns mounted over or incorporated onto isotropic radiating elements andomnidirectional receiving elements. We will now examine structures thatcan be incorporated into a phased array antenna system electromagnetictransmitting pathway to create non-isotropic radiating elements andnon-omnidirectional receiving elements that are embodiments of thisinvention.

One key requirement in constructing the array of non-isotropic radiatingelements of embodiments of this invention, is the tightly packing of theradiating elements in many arrays. In typical radar phased arrays,radiating elements are spaced from 0.5 to 1.0 wavelength. One structurethat can be applied to each radiating element in an array of radiatingelements to focus each radiating element into a non-isotropic radiatingelement is a lens. Prior art phased array antenna, including US3755815,Stangel et al and US4381509A, Rotman et al, utilized one lens to focusthe radiated waves of an array of radiating elements in the horizontaland vertical plane narrowing the field of view and increasing gain inthe field of view. These lenses focus the radiating beam in both thehorizontal and vertical planes, taking a generally isotropic radiatingelement with a field of view of at least +/−60° and forming focused beamwith a field of view of for example +/−10° to +/−20° in both azimuth andelevation. But these antenna systems cannot be used to address a full+/−60° or +/−90° field of view required in most phased array antennasystems and demonstrated in the prior art phased array radar system inExample A.

A cylindrical lens with curvature in just the vertical plane or in justthe horizontal plane can be used to form a radiated wave with focusingin just the vertical plane or in just the horizontal plane. There aretwo types of lenses that have been used to provide plane-wavefront,narrow beams: conducting type lenses and dielectric type lenses. Aconducting type lens has flat metal strips placed in the lens dielectricmaterial in parallel to the electric field of the wave and spaced atslightly larger than one-half wavelength within a dielectric material. Adielectric lens is composed of a high dielectric constant organic orinorganic material. In both of these lens types, the dielectric materialis effectively transparent to the electromagnetic waves but thedifference in the lens dielectric constant or the index of refractionverses air causes the wave to either converge or diverge based upon theshape of the lens.

A cylindrical versions of a conductive lens that can be used to formnon-isotropic radiating elements from an array of isotropic radiatingelements are depicted in FIGS. 19A through 19C according to anembodiment of this invention. FIG. 19A depicts a perspective view of acylindrical version of conducting type lens 300. Metal strips 302 withinthe lens 300, are horizontal and act as wave guides that force theradiated waves to propagate horizontally, parallel to the metal strips302. Lens face 304 is concave in the vertical direction and parallel inthe horizontal direction. The opposite face 306, facing away from theradiating element, is flat in the vertical direction and in thehorizontal direction. This type lens would only beam form in thevertical plane and not in the horizontal plane. FIG. 19B depicts thevertical cross-section of conductive lens 300 containing metal strips302. Concave lens face 304 faces isotropic radiating element 308.Isotropic radiating element 308 has a spherical radiating wave front310. The velocity of the phase propagation of the wave is greater in theconductive lens than in air so that the radiated wave front 312 withinlens 300 and the radiated wave 316 exiting the lens rear face 306 islinear in the vertical plane. Cylindrical lens 300 is concave on theface 304 toward radiating element 308 in the vertical plane so the outerportions of the transmitted spherical waves are accelerated for a longerdistance and therefore for a longer interval of time then the innerportion. The radiated wave enters the lens concave surface as aspherical waves and exits the the flat rear face 306 of the lens asflat-fronted parallel wave in the vertical plane with a narrow verticalbeam width. FIG. 19C depicts the horizontal cross-section of conductivelens 300. Isotropic radiating element 308 has a spherical radiating wavefront 310. In the horizontal plane the metal strips do not affect thewave direction and in the horizontal plane, the wave emerges from thelens rear face 306 in the same radiating directions and with a circularwavefront 316. It should be noted that the conducting lens is frequencysensitive and therefore not applicable to a dual frequency antenna.

FIGS. 20A through 20C depict a cylindrical version of dielectric typelens according to an embodiment of this invention. FIG. 20A depicts aperspective view of a cylindrical version of dielectric type lens 320. Aface of the dielectric lens 324 that faces toward the radiating elementis convex in the vertical direction and linear in the horizontaldirection. The opposite face 326, facing away from the radiatingelement, is flat in the vertical direction and in the horizontaldirection. The dielectric material in the lens 320 refracts the wavesentering it and slows down the phase propagation as the wave passesthrough it. FIG. 20B depicts a vertical cross-section of dielectric lens320. It has isotropic radiating element 308 that has a sphericalradiating wave front 310. Focusing in the vertical plane occurs as theportions of the radiated spherical wave front 310 hits the lens face 324at different points, with different angles to face 324 and at differentphases than other portions of the wave. This causes the spherical waveto form a linear wave front 332 in the vertical plane within the lensand to exit the lens as flat-fronted parallel wave 334 in the verticalplane. In this example, the inner portions of the wave are slowed for alonger time than the outer portions. FIG. 20C depicts a horizontalcross-section of lens 320. It has isotropic radiating element 308 thathas a spherical radiating wave front 310. Although the higher dielectricconstant of the lens dielectric material does bend the incident wave andslow the wave propagation, because the input face 324 and the outputface 326 are parallel in the horizontal plane, there is no beam focusingin the horizontal plane. The exiting wave front 336 is circular in thehorizontal plane.

FIGS. 21A through 21C depict a cylindrical version of another dielectrictype lens according to an embodiment of this invention. FIG. 21A depictsa perspective view of a cylindrical version of dielectric type lens 340.The face of the dielectric lens 344 that faces toward the radiatingelement is flat in the vertical plane and in the horizontal plane. Theopposite face 346, facing away from the radiating element, is convex inthe vertical plane and linear in the horizontal plane. The dielectricmaterial in the lens 340 slows down the phase propagation as the wavepasses through it. FIG. 21B depicts a vertical cross-section ofdielectric lens 340. It has isotropic radiating element 308 that has aspherical radiating wave front 310. Focusing occurs as the portions ofthe radiated spherical wave front 108 hits the lens face 342 atdifferent points, a different angles to lens face 342 and at differentphases than another portion of the wave. The lens face 344 causes thespherical wave to form a modified spherical wave front 356 in thevertical plane within the lens. Additional focusing occurs when the wavefront exits the outer face 346 of lens 340. The net effect ofcylindrical lens 340 is that the radiated wave exits lens face 346 asflat-fronted parallel wave 354 in the vertical plane. In this example,the inner portions of the wave are slowed for a longer time than theouter portions. FIG. 21C depicts a horizontal cross-section of lens 340.It has isotropic radiating element 308 that has a spherical radiatingwave front 310. Although the higher dielectric constant of the lensdielectric material does bend the incident wave and slow the wavepropagation, because the input face 344 and the output face 346 areparallel in the horizontal plane, there is no beam focusing in thehorizontal plane. The exiting wave front 358 is circular in thehorizontal plane.

One preferred embodiment of this invention would utilize lenses to formthe non-isotropic radiating array elements of Example G above. Thelenses would be horizontal cylindrical lenses, either conducting ordielectric type lens, that focuses only in the vertical plane, andleaving the horizontal plane without any focusing. Depending on thecharacteristics of the horizontal cylindrical lenses and the position ofeach of the radiating elements relative to each lens, the degree of beamfocusing in the vertical direction can be varied from an incident wavebandwidth of +/−60° to a radiated wave bandwidth of as low as +/−2° toperhaps +/−10° or even as wide as +/−20°. It should be note that thenarrower the radiated beam width exiting the lens, the higher the powerdensity of the wave within the beam. The lens used to focus the radiatedwave for Example G would have a horizontal radiated wave field of viewof +/−60° and a vertical radiated wave field of view of 0° to +6°.

There are many different lens sizes, shapes and dielectric material thatcould be used for the dielectric type cylindrical horizontal lens andmany ways to attach the lens to implement the embodiment of thisinvention contained in Example G or in other embodiments of thisinvention. The dielectric cylindrical horizontal lenses depicted in FIG.20A and FIG. 21A could be lenses that are designed to be mounted overeach radiating element with each radiating element having its own lens.The phased array of Example G has 500 non-isotropic elements in an arrayof 20 rows of 25 elements per row. If individual lens were used, itwould require 500 lenses to be mounted on the array, one over eachelement. Alternatively, long rectangular shaped horizontal cylindricallenses can be mounted in the wave path of multiple radiating elements orin the path on a whole row of radiating elements. If a lens is designedto cover five elements, then the array would require five lenses per rowand 100 for the whole array. FIG. 22A depicts the portion of a phasedarray antenna 360 with 500 radiating elements in an array of 20 rows of25 elements per row according to an embodiment of this invention ofExample G. Note that the 500 isotropic radiating elements of Example Gare not depicted in FIGS. 22A and 22B for clarity. There are fivehorizontal cylindrical lens 362 per row each covering five elements, fora total of 100 lenses. Going a step further, if each lens is designed tocover all 25 element in a row, then only 20 lenses would be required oneper row. FIG. 22B depicts the portion of a phased array antenna 370 with500 radiating elements in an array of 20 rows of 25 elements per rowaccording to an embodiment of this invention. There is one horizontalcylindrical lens 372 per row, for a total of 20 lenses each covering 25elements.

Another lens technology that can be used to form the non-isotropicradiating waves is the use of lenses using metamaterials which arecomposed of man-made composite materials having a negative index ofrefraction as described in US2005/225492 Metz. Those skilled in the artwould recognize that many other cylindrical conductive and dielectriclens structures could also provide the desired beamforming and providethe non-isotropic radiating elements of preferred embodiments of thisinvention as detailed in Example G or other examples detailed in thisspecification.

Another structure that can have focusing in the horizontal and/orvertical direction is radiating elements utilizing a horn structure.Horn structures can come in many forms such as square horns that flareequally in height and width or rectangular horns that are flared in onlyone dimension. FIGS. 23A and 23B depicts prior art rectangular hornstructures used to form non-isotropic radiated pattern from a isotropicradiating element. FIG. 23A depicts a typical rectangular horn antennawhich flares only in the vertical direction and is an E-plane horn. FIG.23B depicts a typical rectangular horn antenna which flares only in thehorizontal direction and is an H-plane horn. FIGS. 23C and 23D depictthe horizontal and vertical gain plots respectively for the H-plane hornin FIG. 23B. FIG. 23C depicts the horizontal gain plot which has minimumamount of horizontal beam forming. FIG. 23D depicts the vertical gainplot which has a significant amount of beam forming. The horizontaldirection or H-plane horn could be used to form the non-isotropicradiating elements that address the remote field from Example G above.As one skilled in the art understands, H-plane horn could be design witha sidewall slope and with specific length and internal dimensions basedof the wave length(s) of the electromagnetic signal(s) and the degree ofhorizontal and vertical beamforming desired.

The rectangular horn of FIG. 23B represents a singular radiating elementthat would typically be used to feed a parabolic reflecting antenna. Inan array of 100's or 1000's of radiating elements, the use of individualconstructed horns may not be practical or even possible. A morepractical approach would be to use MEMS like photo-processing tofabricate arrays of horn structures in situ or to fabricate strips ofreflecting structures that form an array of horizontal micro-horns.FIGS. 24A through 24C depict three views of a portion of an antennaarray 380 of isotropic radiation elements utilizing in situ fabricatedmicro-horn structures to form non-isotropic radiating elements accordingto an embodiment of this invention. FIG. 24A depicts a portion of theradiating front of the antenna array 380 with four radiating elements382 in each of two rows. FIG. 24B depicts a horizontal cross-section ofthe antenna cut through the radiating elements 382 in one row. FIG. 24Cdepicts a vertical cross section of the antenna cut through theradiating elements 382 in one column. As seen in FIG. 24B, thehorizontal cross-section has sloped reflecting surfaces 384 formingflared horizontal horn portions. As seen in FIG. 24C, the verticalcross-section has non-flared vertical reflecting surfaces 386. Thisstructure can be formed by applying a thick photo-patternable dielectricof photoresist, forming a cavity to each radiating element with straightsidewalls on the top and bottom sides of the opening and with slopedsidewalls of the left and right sidewalls. The sidewall surfaces couldbe coated with a metal layer to form the reflective surfaces.

Those skilled in the art would recognize that many other micro-hornstructures and fabrication methods could also provide the desired hornstructure and provide the non-isotropic radiating elements fromisotropic radiating elements according to an embodiment of thisinvention.

FIG. 25 depicts an example of a cellular tower linear array antenna withcylindrical lenses mounted over isotropic radiating elements for theline array of Example I. In this example of an embodiment of thisinvention, the cellular tower linear array depicted in FIG. 7 from priorart baseline Example C is modified to achieve non-isotropic radiatingelements. The transmitting line array antenna has eight isotropicradiating elements 202 located on the face 204 of the antenna (the sameas the prior art antenna of FIG. 7). One cylindrical lens 402 such ascylindrical lens 320 depicted in FIG. 20A, is mounted over or formed oneach array radiating element. Each cylindrical lens 402 has verticalconvex curvature facing away from the face 304 to focus the isotropicradiated waves vertically and form narrow non-isotropic radiatingelements in the vertical plane. It has no horizontal curvature and thusdoes not focus horizontally. Each lens forms a focused beam in thevertical plane at least as broad as the vertical beam width in the priorart array in Example C, +/−10°.

Phased Array Receiving Elements

In the example of antenna system of an embodiment of this invention inExample G, the discussion only addressed the effects of utilizing bothisotropic radiating elements and non-isotropic radiating elements in aphased array radar antenna. The maximum detection range R_(max) in theprior art phased array radar antenna of Example A was increased by 78%in Example G with the same number of elements and with the sameradiating power per element. We will now consider the effects of theantenna of Example G on the receiving elements according to anembodiment of this invention in Example J. The return waves or signalsreflected off of a target and received back at the antenna. Thereflected signals return on the same elevation and horizontal directionas the original transmitted wave. If the antenna utilizes a lens tofocus the radiated wave from each isotropic radiating element to formnon-isotropic radiated elements, then the return wave would return onthe same path and would be focused back onto the receiving element onthe reverse pathway as it was on the transmitted electromagnetic wave.In Example J the focusing effect of the lens system would increase thepower level of the return signal received by each receiving element by afactor of 4 X to 8 X providing 6 dB to 9 dB increase in antenna receivergain. That would effectively increase the maximum range R_(max3) by afactor of 1.4 X to 1.6 X over the antenna gain of Example G. Combiningthe increased antenna receiver gain with increased antenna transmitgain, the R_(max) would increase the antenna maximum range by a factorof 2.5 X to 3.0 X over the prior art radar system of Example A. Theantenna system of the prior art in Example A had an R_(max) of 150 km.The increased antenna transmit gain of 10 dB in Example G, over thebaseline of Example A extends R_(max) from 150 km to 267 km. Factoringin the increased antenna receiver gain of 6 dB to 9 dB, R_(max) would beextended from the prior art base line of 150 km to 375 km to 450 km.This is an increase in R_(max) of more than double the original R_(max)of 150 km of the baseline antenna of Example A, while having the samenumber of antenna elements, 1000, and having the same radiated power perradiating element and the same receiver element capability.

Acoustic Phased Array Antenna Systems

The concept described above relative to electromagnetic phased arrayradar antenna to increase its R_(max), can be applied to an active orpassive sonar system to increases the sonar maximum range, R_(max). Anexample of an embodiment of this invention is the phased array sonarsystem of Example K. The sonar phased array system in Example K has thesame number, type of transducers and the same output power per elementas the sonar system phased array in Example D but it has 200 isotropictransducer elements covering non-remote field targets and 200non-isotropic transducer elements covering remote field targets. The 200isotropic radiating elements have a transmitting gain of 23 dB, 3 dBless than the 400 element system of Example D. The isotropic elementshave a field of view of +/−90° in azimuth and +/−90° in elevation. Thereceiving gain of this portion of the sonar phased array system would be23 dB (based upon its 200 isotropic receiving elements). The total sonarantenna gain would be the combined antenna transmit and receive gain or46 dB (23 dB transmit gain and 23 dB receive gain) with R_(max) of 106km, a 29% reduction from the baseline of Example D. Beams formed fromthese 200 isotropic elements are used for detecting targets in thenon-remote field, from the sonar antenna to 106 km.

The 200 non-isotropic transducer elements have vertical focusing thatnarrows the resulting beam to an elevation field of view +/−4.5° whilekeeping the azimuth field of view to +/−90° targeting the remote field.The 200 non-isotropic transducer elements have an antenna transmit gainof 23 dB (based on its reduced number of emitting elements). Thefocusing of the transmitted beam from the non-isotropic transducerelements vertically from the initial field of view of +/−90° to +/−4.5°,increases the power density by a factor of 20 within the beam for a 13dB increase in gain. This would provide a net transmission gain of 36 dB(23 dB antenna plus 13 dB focusing). It also lowers the side lobesoutside of the field of view. The focusing of the returned acousticsignal by the non-isotropic transducer elements in elevation from theinitial field of view of +/−90° to +/−4.5° of the focused field of view,increases the power density of the return signal by a factor of 20 foracoustic waves within the beam path for a 13 dB increase in antennareceiver gain. This would provide a net receiver gain of 36 dB (23 dBantenna and +13 dB focusing). The total sonar antenna gain would be thecombined antenna transmit and receive gain or 72 dB (36 dB transmit gainand 36 dB receive gain) a 20 dB increase over the baseline sonar ofExample D. This increases R_(max) from the 15 km of Example D to 47 kmof Example K, an increase in R_(max) of 213%.

The non-isotropic acoustic elements for a sonar system can be achievedby attaching a lens over each transducer element to focus thetransmitting beam into a wavefront with a 9° vertical field of view andthe full 180° horizontal field of view. For smaller acoustic systemssuch as a medical or industrial ultrasound system, an array ofmicro-lens formed in situ would be a better option.

Example L is a passive towed array system according to an embodiment ofthis invention which has 1000 transducer elements, 500 omnidirectionaltransducers and 500 non-omnidirectional transducers. The 500omnidirectional transducers are identical to the omnidirectionaltransducers of Example E with the same sensing threshold. The 500omnidirectional transducers have a gain of 27 dB, 3 dB less than the1000 transducers in Example E. They are used to sense targets in thenon-remote field from 0.84 R_(max4) and closer in. The 500non-omnidirectional transducers have an antenna gain of 27 dB. The 500non-omnidirectional transducers have focusing structures on eachreceiving element focus acoustic signals and reduce the sensing field ofview to +/−4.5° vertically and while maintaining the same +/−90°horizontal field of view as in the prior art system of Example E. Thisincreases sensing gain from signals from within the narrower envelope by20 to 1, or 13 dB per sensing element. The total gain of the 500non-omnidirectional sensors is 40 dB (27 dB antenna gain plus 13 dBfocusing gain). This increases the maximum sensing range for thenon-omnidirectional elements in its field of view by a factor of 3.16 Xmore than tripling R_(max4) of the system. It should be noted that therange equation for a passive acoustic system such as a passive towedarray goes by the second power not the fourth power as with active sonarwhere pulses must travel from the transducers to the target and backwhereas passive sonar signals only travel from the target to thetransducers.

Although only two examples of acoustic phased array systems aredescribed above, the embodiments of this invention relative to theexample acoustic systems detailed here equally applies to other acousticsystems such as ultrasound, geological acoustic systems and other typesof phased array acoustic systems. One skilled in the art could apply theprinciples of this invention to many other acoustic phased array activeand passive systems.

Optical Phased Array Systems

Another embodiment of this invention is an optical phased array systemwith both isotropic and non-isotropic radiating elements and/or withomnidirectional and non-directional optical imaging elements. The sameconcept described above relative to a phased array radar antenna and aphased array sonar system can be applied to the optical phased arraysystem. Example M is an optical phased array system of an embodiment ofthis invention that is similar to the prior art optical phased arraysystem of Example F. Example M is an optical phased array system with100 light emitters in an array of 10 rows with 10 elements per row. Theantenna gain is 20 dB and its R_(max) is 150 km when using all 100elements. It has 50 isotropic elements covering non-remote field regionsand 50 non-isotropic elements with a horizontal focusing covering remotefield regions. The focusing narrows the resulting field of view fromeach non-isotropic element to elevation 0° to 6° while keeping theazimuth field of view to +/−60°. The reduction in the number ofisotropic transmission elements from 100 to 50 used for the non-remotefield, reduces the antenna gain for the isotropic portion of the antennaby 3 dB to 17 dB. The reduction in the number of transmission elementsfrom 100 to 50 used in the non-isotropic elements for the remote field,reduces the antenna gain for the non-isotropic portion of the antenna by3 dB to 17 dB. The beam focusing increases the optical power density bya factor of 20 within the beam, a 13 dB increase, and lowers the sidelobes outside of the field of view. The net antenna gain increase forthe 50 non-isotropic emitting elements would be would be 10 dB (−3 dBlower radiating elements and +13 dB increased beam power densityincrease) and would increase R_(max) from the 150 km of the baseline to267 km, an increase of 78%. This same focusing system would improve theperformance of the receiving element by focusing the return signalsproportionally. The reduction of receiving elements from 100 to 50 usedin the non-isotropic elements for the remote field, reduces the antennareceive gain by 3 dB. The focusing of the received signal increases theoptical receive signal sensitivity by a factor of 20, 13 dB increase.The net antenna receiving gain would be 10 dB (−3 dB due to fewersensing elements and +13 dB increased in return signal power density).Combining increase in both the transmission gain, 10 dB and thereceiving gain, 10 dB, the increased system gain is 20 dB which wouldincrease the R_(max) to 474 km, an increase of 216%.

The transformation of the isotropic light emitting elements into theproposed non-isotropic light emitting elements can best be accomplishedby forming micro lenses over each to the elements. Examples of opticalphased array systems use semiconducting array chips with 100's or 1000'sof optical nano-emitter elements on a grid on 10 to 100 microns⁸. Atthese dimensions, mounting a separate lens over each element isimpractical at best. One option is to use micro-fabrication techniquesto form micro-lenses from dielectric material directly on the devicesurface. FIGS. 26A through 26E depict one method for the formationcylindrical lens over the emitting elements that is an embodiment ofthis invention. The cylindrical lens has a vertical concave surface tofocus the emitted light in the vertical plane and has a flat horizontalsurface that does not focus the emitted light in the horizontal plane.FIG. 26A depicts a vertical cross-section of an antenna segment prior tothe formation of the in situ lenses. The antenna face 404 has tworadiating elements 406 on its outer surface. FIG. 26B depicts theantenna segment after support walls 408 are formed between eachradiating element 404. Support walls 408 can be composed of a metal ordielectric material. FIG. 26C depicts the antenna segment after firstresin 410 is deposited over the surface between support walls 408 andcured. First resin 410 can be a photoresist or a photo-patternable resinsuch as SU-8. FIG. 26D depicts the antenna segment after first resin 410is etched to form circular trench 412 by photo-etching or laserablation, for example. FIG. 26E depicts the antenna segment afteroptical resin 414 is applied over first resin 410 and support walls 408and cured. Optical resin 414 is preferably a clear resin with a highindex of refraction such as PMMA (1.49), PET (1.57), polycarbonate (1.6)for example. In some applications, first resin 410 is preferably aremovable resin that is removed by etching or by sublimation. This wouldprovide an air dielectric of the antenna side of the cylindrical lens.Alternatively, first dielectric 410 can be a permanent dielectric with alow index of refraction such as Teflon AF (1.32) or perfluorohexane(1.25) for example. FIG. 27 depicts a ray diagram for the in situcylindrical lens 416 shown in FIG. 26E where first resin 408 is left inplace. FIG. 28 depicts a ray diagram for the cylindrical lens 418 afterfirst resin 208 is removed leaving air dielectric 420 on the innersurface of the optical resin 414.

FIG. 29 depicts another cylindrical lens structure 430 with its raydiagram. The outer surface 432 of optical resin 414 sculptured to form acylindrical outer surface that matches its cylindrical inner surface. Ithas the first resin 410 in place as the antenna segment depicted in FIG.23. FIG. 30 depicts yet another cylindrical lens structure 440 and itsray diagram. The outer surface 432 of optical resin 414 sculptured toform a cylindrical outer surface that matches its cylindrical innersurface. It has the first resin removed to form an air dielectric 420 onthe inner surface of the optical dielectric 414.

Although not covered in the above discussion nor in the above figures,the same lens focusing elements can be added to optical receivers of anoptical phased array antenna. The same types of lenses and theprocessing steps used to create the lens structure for the transmittingelement above can be applied to create a plurality ofnon-omnidirectional optical receiving elements by forming micro-lensesover an array of omnidirectional optical receivers forming an embodimentof this invention. Similarly, the in situ formed lenses depicted inFIGS. 26 30 can be applied to form focusing lenses and phased arrayradar systems and on acoustic phased array systems. The dimensions ofthe lenses would change based on the pitch of the radiating and/orreceiving elements and on the wavelength of the emitted and/or receivedwaveform.

Although only one example of optical phased array systems is describedabove, the embodiments of this invention relative to phased arrayoptical systems equally applies to other phased array optical systemssuch as communication systems, imaging systems and other types of phasedarray optical systems. Ones skilled in the art could apply theprinciples of this invention to many other optical phased array systems.

Antenna Face Orientation

In many prior art phased array antenna systems, the face of the antennais offset from vertical to optimize the gain plot of the antenna toenable beam forming past vertical such as for example a 10° tilt. If forexample, the non-isotropic radiating elements have a field of view fromantenna broadside of +/−3° in elevation, forming a 6° beam width inelevation, then the field of view of the non-isotropic radiatingelements needs to be tilted from the antenna broadside in order totarget objects in the remote field in a narrow elevation range from 0°elevation to a few degrees above, such as from the horizon to about 3°to 6° above the horizon. Even an antenna without tilt might require thefield of view of non-isotropic radiating elements to be off-set from theantenna broadside to center the field of view of the elements to thedesired elevation range.

If lenses or horn structures are used to form the non-isotropicradiating elements from generally isotropic radiating elements and theyare mounted directly over the isotropic radiating elements, then theresulting non-isotropic beams would be focused at 90° from the antennaface or at the antenna broadside. This would be the case for the lensstructures depicted in FIGS. 19, 20 & 21 above if the antenna face isoffset from vertical. A preferred approach to adjust the narrow verticalfield of view of the non-isotropic radiating elements of embodiments ofthis invention is to offset the lenses used to narrow the field of viewfrom the isotropic radiating elements vertically.

FIGS. 31A and 31B depict cross-sections of cylindrical lenses that areoffset from the face of the antenna to optimize the field of view of theresulting beam to focus on the remote field near zero elevation as anembodiment of this invention. FIG. 31A depicts a portion of an radiatingantenna array 460 that has an angular tilt of the antenna face 462 of+θ¹° from vertical. Cylindrical conducting lens 300 is similar tocylindrical conducting lens 300 depicted in FIG. 19B. It has a concaveface 304 facing radiating element and flat face 306 facing away from theradiating element. Conductive lens 300 contains metal strips 312 runninghorizontally. Antenna face 462 is offset by θ²° from the orientation ofthe antenna face 462. Isotropic radiating element 306 has a broad sideangle of θ¹° from horizontal. It has a spherical radiating wave front308 which impinges of the concave lens face 304. Parallel wave front 314radiates from the far side 306 of cylindrical conducting lens 300parallel to the lens side 304. It is offset from the antenna face 262 byθ²° and would be offset from horizontal by θ¹°-θ²°.

FIG. 31B depicts a portion of an radiating antenna array 470 that has anangular tilt of the antenna face 472 of +θ¹° from vertical. Cylindricaldielectric lens 320 is similar to cylindrical dielectric lens 320depicted in FIG. 20B. It is offset by θ²° from antenna face 472.Isotropic radiating element 308 has a broad side angle of θ¹° fromhorizontal. It has a spherical radiating wave front 310 which impingesof the convex lens face 324. Within lens 320 the radiated wave front 32is parallel with the far face 326. Parallel wave front 334 exits the farface 332 of lens 320 is offset from the antenna broadside by θ²° andwould be offset from horizontal by θ¹°-θ²°. The resulting radiatingbeams from radiating antenna array 460 and radiating antenna array 470are focused near zero elevation to target the remote field near thehorizon.

The same lens offset depicted in FIGS. 31A and 31B can be used onacoustic and optical phased array antenna to specifically direct thenon-isotropic radiating elements to a desired elevation rather thanbroadside to the antenna face. For example, a communication phased arrayantenna system located on a high tower or on a hill top might have itsantenna broadside targeted below horizontal. In an embodiment of thisinvention, the antenna could have a portion of the radiating elementshaving a generally isotropic radiating pattern that covers a +/−60°azimuth and a −20° to +90° elevation covering non-remote fieldcommunication receivers and transmitters and would have the balance ofthe radiating elements having a non-isotropic radiating pattern focusednear the horizontal at an offset angle from the antenna broadside andcovering remote field communication receivers and transmitters.

In those embodiments of this invention where all antenna elements arenon-isotropic radiators or non-omnidirectional receivers, the antennaitself can and generally would be, tilted to optimize the center oftheir field of view to the desired elevation so it would not be requireto tilt the lenses or micro-horns.

Other Aspects of this Invention

Most of the radar, sonar and optical array examples of embodiments ofthis invention described above were examples where 50% of the radiatingelements of the various phased array antenna were isotropic radiatingand/or omnidirectional receiving elements and 50% were non-isotropicradiating and/or non-omnidirectional receiving elements. Many otherratios of isotropic and non-isotropic radiating elements and/oromnidirectional and non-omnidirectional receiving elements can be usedto implement embodiments of this invention. In Example G, the radarsystem with a 1000 element array had 500 isotropic radiating elementsand 500 non-isotropic radiating elements, a 50:50 mix. The radar systemcould have had fewer than or more than 500 non-isotropic radiatingelements. There is a trade-off that can be made to increase thenon-remote field power density and decrease the remote field powerdensity and lower R_(max) by having for example 750 isotropic radiatingelements and only 250 non-isotropic radiating elements. The non-remotefield R_(max) would increase from 126 km to 139 km while the remotefield would decrease from 267 km to 224 km. Similarly, a trade-off couldbe made to further increase the remote field R_(max) of thenon-isotropic radiating elements at the expense of the decreasingfurther the non-remote field power density and the R_(max) of theisotropic radiating elements by having for example only 250 isotropicradiating elements and 750 non-isotropic radiating elements. Thenon-remote field R_(max) would decrease from 126 km to 106 km while theremote field would decrease from 267 km to 295 km. The embodiments ofthis invention apply to any ratio of directional and non-directionalphased array elements.

Further, other variations of the specific details of the phased arrayelements of embodiments of this invention include for example having awider or narrower remote field of view formed by the non-isotropicradiating elements and/or the non-omnidirectional receiving elements.Changing the remote field elevation field of view of the phased arrayradar antenna of Example G from 6° to 9° would decrease its gain by 1.8dB and decrease R_(max) from 267 km of Example G to 240 km. That isstill represents a 60% increase in R_(max) over the base line R_(max) ofantenna of Example A, 150 km. In the case where a narrower field of viewis formed, such as one having 4° vertical field of view, the gain wouldbe increased by 1.8 dB and the R_(max) would be increased to 300 km.

A still further embodiment of this invention is a phased array antennasystem in which the generally isotropic radiating elements used inaddressing the non-remote field have a small degree of focusing appliedto their radiating pattern. In the case of a surface ship phased arrayradar system such as the prior art radar system described in Example A,all radiating elements are isotropic with a field of view of at least+/−60° in azimuth and least +/−60° in elevation. The radar system ofExample G incorporating embodiments of this invention with half ofantenna having non-isotropic radiating elements that extend R_(max) by78%. Although the non-remote field isotropic radiating elements ofExample G have an elevation field of view of +/−60°, the only usefulportion is from horizontal (0°) to just over vertical (90°). If thenon-remote field isotropic radiating elements had minimum focusing sothat the elevation field of view were reduced from the prior art +/−60°to a narrower 0° to 100° by using for example with a cylindrical lenswith minimum curvature, the power level in the reduced field of viewwould be increased by 20% providing an additional gain of 0.8 dB.

FIGS. 32A through 32C depict a dielectric lens that could be used tofocus the non-remote field radiating elements field of view from morethan 120° down to 90° for example. Cylindrical lens 520 is similar tocylindrical lens 320 depicted in FIGS. 20A through 20C except it hassignificant less curvature. FIG. 32A depicts a perspective view of lens520. It is convex on face 524 which faces the antenna face and flat onthe opposite face 526. Lens 520 has less curvature on face 524 versusface 324 of lens 320. FIG. 32B depicts a vertical cross-section of lens520. Isotropic radiating element 508 radiates a spherical wave front 510that impinges of lens face 524. The lens face 524 refracts the radiatedwave but less than lens face 324 in FIG. 20B. The radiated wave frontexits the lens on face 526 with a curved wave front that is neither flatnor fully spherical. The radiated wave would have a beam width 20% to25% narrower than the initial spherical wave front 510 and would have apower density within the beam of 20% to 33% higher. This would increasethe non-remote field R_(max) by 10% to 20%. FIG. 32C depicts thehorizontal cross-section of lens 520. It has the same effect on radiatedwave 510 in the horizontal plane as does lens 320 in FIG. 20C, i.e.having the radiated wave front 534 exiting lens face 526 as a sphericalwave front in the horizontal plane.

Yet another implementation of embodiments of this invention is a phasedarray antenna system having a plurality generally isotropic radiatingelements and a plurality of non-isotropic radiating elements where thenon-isotropic radiating elements have a narrower field of view in boththe vertical plane and the horizontal plane. In the automotive phasedarray radar system of prior art Example B and the version in Example Hincorporating embodiments of this invention, the radiating area arrayantenna for the remote field only covers an area of +/−9° in azimuthfrom antenna broadside and 0° to 9° in elevation. In Example H, theremote field radiating elements have focusing elements such ascylindrical lenses to narrow the radiated horizontal field of view fromthe initial +/−60° to +/−9° in the modified version base on embodimentsof this invention. This increased the radiated power density in theremote field by a factor 6.7 X and a gain increase of more than 8 dBwhile covering the same field as the automotive radar of Example B.

In Example N, an additional embodiment of this invention is applied tothe antenna of Example H, whereby the remote field radiating elementshave their vertical field of view narrowed as well. The remote fieldvertical field of view is reduced from the original +/−60° of Example Band modified Example H to 0° to 9° in elevation to match the requiredremote field horizontal field of view. This would increase the radiatedpower density in the remote field by an additional factor of more than13 X for an additional gain of 11 dB. The combined 19 dB increase in theradiated power density within the narrower field of view of 0° to +9°vertically and +/−9° horizontally would increase the maximum range by 3X or from the 250 m of Example B to 750 m in Example H. In this case,with no increase in radiating element power, no change in the number ofradiating elements and no loss of scanned field of view, the remotefield maximum range would be increased by a factor of 3 X or more.

Although a range increase from the baseline 250 meters on an automotivedrive assist radar system may not highly useful, the increased antennagain provided by embodiments of this invention can be used to reduce thecost of the antenna system by lower the element power or by reducing thenumber of antenna elements.

FIGS. 33A through 33C depict oval lens 540 in prospective view, verticalcross-section and horizontal cross-section that can form the verticaland horizontal wave focusing of automotive phased array radar of ExampleN in this embodiment of this invention. FIG. 33A depicts a perspectiveview of oval lens 540 that has curved face 544 that would face theantenna face and has flat face 546 on the lens opposite side. FIG. 33Bdepicts the vertical cross-section of oval lens 540. Isotropic radiatingelement 308 radiates spherical wave front 310 which impinges on thecurved surface 544 of oval lens 540. The lens face 544 refracts theradiated wave but less than lens face 324 in FIG. 20B. The radiated wavefront exits the lens on face 546 with a curved wave front that isneither flat nor fully spherical. The radiated wave would have avertical beam width that was 92% narrower than the initial sphericalwave front 510 and would have a power density within the beam of 13 Xhigher for a 11 dB gain FIG. 33C depicts the horizontal cross-section ofoval lens 540. Isotropic radiating element 308 radiates spherical wavefront 310 which impinges on the curved surface 544 of oval lens 540. Thelens face 544 refracts the radiated wave but less than in the verticalplane. The radiated wave front exits the lens on face 546 with a curvedwave front that is neither flat nor fully spherical but with morecurvature than the wave in the vertical plane. The radiated wave wouldhave a horizontal beam width that was 85% narrower than the initialspherical wave front 510 and would have a power density within the beamof 6 X higher for an 8 dB gain. The combination of the wave frontfocusing in both the vertical plane and the horizontal plane wouldprovide the gain of 19 dB detailed above for Example N.

This is an example of an embodiment of this invention where radiatingwaves can be beam formed into non-isotropic wave forms in both thehorizontal and vertical plane with no increase in radiating elementpower, no change in the number of radiating elements and no loss ofscanned field of view while increasing the remote field maximum range bya factor of 3 X or more. The non-isotropic elements with the verticalbeam forming to beam width of 0° to +9° and horizontal beam forming to abeam width of +/−9° can be accomplished with an oval lens with morecurvature in the vertical plane than the horizontal plane. This sameembodiment of this invention can be applied to other examples of phasedarray antenna systems where the radiated beam width can be narrowed inboth the horizontal and the vertical planes.

Although the examples detailed above of radar, acoustic and opticalphased array antenna systems have focused on ground based and shipboardantenna systems, the embodiments of this invention are applicable toother phased array antenna system such as an airborne phased array radarsystem. The key difference of any airborne radar system versus a groundbased system is that the airborne system must have a vertical field ofview that covers positive and negative elevations. The airborne phasedarray antenna must have a non-remote field vertical field of view of+/−60° to +/−90° for example. In this embodiment of the invention, theplurality of isotropic radiating elements must each have a beam width ofat least as wide as the required non-remote field, field of view of theantenna system. The remote field, field of view would be narrower butwould also have to vertical field of view that covers positive andnegative elevations. In the example radar system of Example G thatincorporates an embodiment of this invention, the remote field beamwidth is only 0° to +6° in elevation. If the antenna of Example G wereto be an airborne phased array antenna, its remote field would require abeam width of +/−6°. In that case the focusing cylindrical lens wouldneed to have less curvature than the ones in Example G and would end upwith a 2 X wider vertical beam width and a 2 X lower maximum powerdensity within the beam. The R_(max) would be reduced by a factor of20%, reducing R_(max) from 267 km for Example G to 224 km in theairborne system. Although this is a reduction from R_(max) of Example Gthat incorporates an embodiment of this antenna, it is still 50% furtherthan the R_(max) of the base line prior art of Example A.

Key embodiments of this invention are electromagnetic and acousticphased array antenna systems each such antenna having a plurality ofgenerally isotropic radiating elements and a plurality of non-isotropicradiating elements on the same antenna face. FIG. 34 depicts a phasedarray radar antenna 560 comprising eight rows with 16 radiating elementsper row on the antenna face 562. The upper four rows comprise 64isotropic radiating elements 564. The lower four rows comprisenon-isotropic radiating elements 566. In this example, the non-isotropicradiating elements 566 are composed of isotropic radiating elements 564(not shown) and cylindrical lenses 568 that are mounted over eachisotropic radiating element. As described above in earlier examples ofembodiments of this invention, the portion of the phased array radarantenna 560 with isotropic radiating elements 564 and not havingcylindrical lenses 568 are used to address non-remote regions and theportion of the phased array radar antenna 560 with non-isotropicradiating elements 566 which have cylindrical lenses 568 are used toaddress remote regions. The plurality of isotropic radiating elementsand the plurality on non-isotropic radiating elements depicted in FIG.34 may also comprise a plurality of omnidirectional receiving elementsand a plurality of non-omnidirectional receiving elements with thelenses focusing the return signals onto the omnidirectional receivingelements under the lenses.

FIG. 35 depicts a phased array acoustic antenna 570 comprising ten rowsof radiating acoustic elements with two to ten elements per row for atotal of 56 elements. The upper five rows comprise 28 isotropicradiating elements 574. The lower five rows comprise 28 non-isotropicradiating elements 576. In this example, the non-isotropic radiatingelements 576 are composed of isotropic radiating elements 574 (notshown) and cylindrical lenses 578 that are mounted over each isotropicradiating element. As described above in the radar example depicted inFIG. 34, the portion of the phased array acoustic antenna 570 withisotropic radiating elements 574 and not having cylindrical lenses 578are used to address non-remote regions and the portion of the phasedarray acoustic antenna 570 with non-isotropic radiating elements 576which have cylindrical lenses 578 are used to address remote regions.The plurality of isotropic radiating elements and the plurality onnon-isotropic radiating elements depicted in FIG. 35 may also comprise aplurality of omnidirectional receiving elements and a plurality ofnon-omnidirectional receiving elements with the lenses focusing thereturn signals onto the omnidirectional receiving elements under thelenses.

For the purposes of the specification for this invention the term“generally isotropic radiating element” is defined as a radiatingelement that has a field of view of at least 120° in azimuth and a fieldof view of at least 90° in elevation. Further, for the purposes of thespecification for this invention the term “non-isotropic radiatingelement” is defined as a radiating element that has a field of view isless than half of the field of view of the “generally isotropicradiating elements” of the antenna array in either azimuth and/orelevation. Similarly, for the purposes of the specification for thisinvention the term “generally omnidirectional receiving element” isdefined as a receiving element that has a field of view of at least 120°in azimuth and a field of view of at least 90° in elevation. Inaddition, for the purposes of the specification for this invention, theterm “non-omnidirectional receiving element” is defined as a receivingelement that has a field of view is less than half of the field of viewof the “generally omnidirectional receiving elements” of the antennaarray in either azimuth and/or elevation.

While the invention has been described in detail with only a limitednumber of embodiments, it should be readily understood that theinvention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of this inventionhave been described, it is to be understood that aspects of thisinvention may include only some of the described embodiments.Accordingly, the invention is not to be seen as limited by the foregoingdescription, but is only limited by the scope of the appended claims.

What is claimed is:
 1. An acoustic phased array antenna systemcomprising: a first plurality of acoustic receiving elements whereineach element has a generally omnidirectional field of view of at least120° in azimuth and at least 90° in elevation; and a second plurality ofacoustic receiving elements wherein each element has anon-omnidirectional field of view that is less than half of the fieldsof view of said first plurality of acoustic receiving elements inazimuth and/or elevation; wherein: the first plurality of acousticreceiving elements address non-remote field regions and the secondplurality of acoustic receiving elements address remote field regions;each of the acoustic receiving elements of the second plurality ofacoustic array receiver elements comprises an acoustic receiver having agenerally omnidirectional field of view and a lens to focus the receivedacoustic waves onto the acoustic receiver forming a non-omnidirectionalfield of view; and each lens of the second plurality of acoustic arrayreceiver elements is a cylindrical lens that focuses acoustic waves inthe vertical plane and generally does not focus the acoustic waves inthe horizontal plane.
 2. The acoustic phased array antenna system ofclaim 1 wherein each element of the second plurality of acousticreceiving elements is non-omnidirectional in the vertical plane andgenerally omnidirectional in the horizontal plane.
 3. The acousticphased array antenna system of claim 1 wherein the first plurality ofacoustic receiving elements and the second plurality of acousticreceiving elements are linear arrays or area arrays.
 4. The acousticphased array antenna system of claim 1 wherein each lens of the secondplurality of acoustic array receiver elements is an oval lens thatfocuses acoustic waves more in the vertical plane and less in thehorizontal plane.
 5. The acoustic phased array antenna system of claim 1wherein the acoustic phased array system is a sonar system.
 6. Theacoustic phased array antenna system of claim 1 further comprising: afirst plurality of acoustic radiating elements wherein each element hasa generally isotropic radiating field of view of at least 120° inazimuth and at least 90° in elevation; and a second plurality ofacoustic radiating elements wherein each element has a non-isotropicallyradiating field of view that is less than half of the fields of view ofsaid first plurality of acoustic radiating elements; wherein: the firstplurality of acoustic radiating elements address non-remote fieldregions and the second plurality of acoustic radiating elements addressremote field regions.
 7. The acoustic phased array antenna system ofclaim 6 wherein each element of the second plurality of acousticradiating elements is non-isotropic in the vertical plane and generallyisotropic in the horizontal plane.
 8. The acoustic phased array antennasystem of claim 6 wherein each of the elements of the second pluralityof acoustic array radiating elements comprises a generally isotropicacoustic radiator and a lens to focus the radiated acoustic waves into anarrow beam in at least one of the horizontal and vertical planes. 9.The acoustic phased array antenna system of claim 8 wherein each lens isa cylindrical lens or an oval lens that focuses acoustic waves in thevertical plane and generally does not focus the acoustic waves in thehorizontal plane.
 10. The acoustic phased array antenna system of claim6 wherein the antenna system is an area array antenna.
 11. The acousticphased array antenna system of claim 6 wherein the antenna system ispart of a drive assist system for a motor vehicle.
 12. The acousticphased array antenna system of claim 6 wherein the antenna system ispart of a sonar system or an ultrasound system.